First results from AIMS beta tool for 157-nm lithography

Abstract

In modern mask manufacturing, a successful defect mitigation strategy has been become crucial to achieve defect free masks for high-end lithography. The basic steps of such a strategy include inspection, repair, and subsequent post-repair qualification of repair sites. For the latter task, actinic aerial image measurements have been proven to be the technique of choice to assess the printability of a repaired site. In the last three years, International SEMATECH in cooperation with Infineon/AMTC-Dresden and SELETE, funded a joint development project at Carl Zeiss to develop an AIMS  tool operating at the 157nm wavelength. The three beta tools were shipped in 2003 to the three beta customer sites. In this paper are presented the first results obtained with these beta tools, including measurements on binary as well as alternating phase shift masks. The technical properties of the tool were discussed with regards to the capability of the tool for defect qualification on photomasks. Additionally, preliminary results of the evaluation of alternating phase shift masks will be discussed, including measurements performed on dense lines-and-spaces structures with various pitch sizes.

The importance of being homogeneous: on the influence of illumination inhomogeneity on AIMS images

“…The simulated contrast is still larger than the measured contrast for the same orientation which is mainly due to flare and crosstalk. 16 Note the fairly constant offset between measurements and simulations for both orientations.…”

“…The still existing difference between the measured data and the simulated data for the same orientation can be attributed to the above mentioned effects such as flare, crosstalk, aberrations, etc. 15,16 which are characteristic for the hardware of any tool and are yet neither strongly reduced (as for e.g. in steppers) nor included in the simulations.…”

“…These are aside the pupil inhomogeneity, e.g., flare, cross-talk or lens aberrations, where the former two are considered to be the major effects. 15,16 To distinguish between these effects from those originating from the pupil inhomogeneity, AIMS TM -images of the same structure were acquired in both vertical and horizontal direction. As flare and crosstalk should be less direction dependent, a comparison between both images gives a good indication of the influence of pupil illumination inhomogeneity.…”

“…[11][12][13][14] However, the matching between AIMS TM results and simulations is often unsatisfactory since the imperfections of the AIMS TM optics are normally not included in simulations (e.g., flare, aberrations, cross-talk, inhomogeneous illumination). 15,16 This discrepancy between simulation and measurement is exemplified in the upper part of Figure 1 on a lines and spaces (referred to as l&s hereafter) pattern for annular illumination † . In addition, the lower part of Figure 1 shows the orientation dependence of the measured contrast of the same lines and spaces pattern, which can be attributed to the inhomogeneous illumination.…”

Simulation of quartz phase etch affect on performance of ArF chrome-less hard shifter for 65-nm technology

“…Nevertheless, the absolute values of measurements and simulations do not match very well. The origins of this are deviations of the real geometry of the area that has been quartz etched and flare that is known to reduce the contrast of AIMS measurements 6 . The impact of flare has not been taken into account in the simulations presented here.…”